Platelet-derived growth factor is believed to be important in the aberrant growth of numerous types of cancers. SU101 inhibits PDGF-mediated signaling via the PDGF receptor. This open-label Phase II trial will assess the safety and efficacy of SU101 in decreasing the PSA in patients with PSA+ prostate cancer. Time-to-treatment, time-to-progression and objective response will be assessed. The relationship between SU101 efficacy and athe expression of PDGF receptors in patient prostate tumor tissue samples and bone marrow biopsies will be determined.